1. Field of the Invention
This invention relates in general to pet doors and, more particularly, to a lockable pet door for installation in a glass patio-type door or window.
2. Background of the Invention
Many pet owners, aggravated by the necessity of having to wake up at odd hours of the night or being interrupted in the middle of household chores in order to allow their pets into or out of the house, find it convenient to install pet doors which allow their cats, dogs or other domestic pets to freely come and go at will. Pet doors of two basic types are known. The first type of pet door comprises a simple, downwardly hanging flap of suitable material installed in a conventional wooden door. This type of pet door is generally satisfactory, except that very often conventional wooden doors are found only in the front portion of the house, where they let out directly onto the street or an unfenced front yard, from which the pet could very easily wander away and get lost, injured, or stolen. For this reason, many people prefer a second type of pet door, which can be installed in a glass door of the type which usually lets out onto a fenced-in deck, patio or backyard area.
Glass patio-type doors generally comprise a pair of panels, including a sliding panel and a stationary panel, each of which consists of a pane of glass having its edges received in a rectangular frame. The frame of the stationary panel is fixed in one side of the doorway, while the frame of the sliding panel is mounted on a track which allows it to be slid from an open position in which it overlies the stationary panel to a closed position in which it covers the other side of the doorway. When the sliding panel is in the closed position, one edge of its frame slightly overlaps the frame of the stationary panel. This edge is provided with a specially formed flange which interlocks with a mating flange provided on the frame of the stationary panel, thus preventing an intruder from lifting the panels sliding out of its track and breaking into the house.
A commonly available pet door for installation in the above-described patio-type door requires that the sliding panel of the door be moved into a partially open position, creating a gap between it and the side wall of the doorway. An adapter panel of plastic or other suitable material is then inserted into this gap to block out drafts and the like. The lower portion of this adapter panel is provided with a downwardly hanging flap of material which allows a pet to pass in and out of the door in much the same manner as in the first type of pet door. One problem with this second type of pet door, however, is that because the sliding panel of the main door remains in a partially open position, the door cannot be locked in the usual manner and the specially formed flange on the edge of its frame is disengaged from the mating flange on the edge of the stationary panel. This makes it easy for an intruder to remove the panel and enter the house. In addition, the adapter panel is unattractive, difficult to store when not in use and destroys the symmetrical appearance of the patio door. Still further, the adapter panel often is not well sealed in the doorway, thus allowing relatively hot or cold outside air to enter the house and increasing household energy costs.
A need exists, therefore, for a new and improved security pet door which overcomes some of the problems and shortcomings of the prior art doors.